The proposed research is designed to investigate the mechanisms by which mammalian sperm are capacitated and undergo the acrosome reaction in vivo. Using the pig as the primary experimental animal, those processes will be studied to determine the requirements under conditions that approach the physiological situation. Attention will be directed toward the sperm plasma membrane (PM) and its surface components. Extensive studies are planned on the lipids and on the proteins within and on the surface of sperm PM. Changes in the lipids of sperm that have been observed during capacitation will be studied further. The localization of the lipid within the sperm and the mechanisms for those changes will be pursued. The phospholipids, glycerides, glycolipids and neutral steroids will receive particular attention. After capacitation in vivo, sperm lipids will be extracted, separated and quantified. Analytical procedures will include analyses of phospholipid hydrolysis products (water-soluble polar compounds, fatty acids, fatty aldehydes), TLC of intact phospholipid, gas chromatography of neutral lipid fatty acids and fatty aldehydes, neutral steroids and sugars hydrolyzed from glycolipids. The proteins in PM and adsorbed on the surface of the PM of epididymal sperm will be separated and characterized. Then, the extent and nature of protein adsorption to the sperm surface from seminal plasma will be determined. Finally, the influence of capacitation on the removal or alteration of those surface proteins will be investigated. Proteins will be separated by column chromatography and electrophoresis. Immunocytochemistry (with the electron microscope) and surface iodination will be utilized for localization of proteins. Proteins will be characterized by solubility properties, molecular weight, amino acid composition and carbohydrate content.